Technical Field
The present invention relates to an optical sheet module. More particularly, it relates to an optical sheet module in which two optical sheets are integrally formed below a reflective polarizing sheet.
Background Art
A liquid crystal display device is a display device that is used in a notebook, a personal computer, a smart phone, a TV, or the like, and its properties have also been improved year by year according to the increasing demand for the liquid crystal display device.
A liquid crystal panel of the liquid crystal display device as a non-light emitting element requires a back light unit due to its structure. The back light unit is constituted by various optical systems. Further, the back light unit uses an optical film of a periodic arrangement in order to improve the brightness.
FIG. 1 is a diagram schematically illustrating a configuration of a liquid crystal display device that has been conventionally developed.
As illustrated in FIG. 1, aback light unit 10 includes a light-emitting source 1, a reflecting plate 3, a light guide plate 2, a diffusion sheet 4, a first optical sheet 5, a second optical sheet 6, and a reflective polarizing sheet 7.
The light-emitting source 1 is an element that generates visible light, and as the light sources 1, it is possible to selectively use a light emitting diode (LED), a cold cathode fluorescent (CCFL), or the like.
Light emitted from the light source 1 is incident on the light guide plate 2 and proceeds while causing the total reflection within the light guide plate 2, and since light incident on the surface of the light guide plate 2 at an incidence angle smaller than a critical angle is transmitted without being totally reflected, the light is emitted to the upper side and the lower side.
At this time, the reflecting plate 3 reflects the light emitted to the lower side and allows the light to enter the light guide plate 2 again, thereby improving the light efficiency.
The diffusion sheet 4 diffuses the light emitted through the top surface of the light guide plate 2 to provide uniform brightness and broaden a viewing angle, and brightness of the light passed through the diffusion sheet 4 is lowered in the vertical direction.
The first optical sheet 5 constituted by a base portion 5b and a structurization pattern 5a primarily condenses and releases the light incident from the diffusion sheet 4 so as to be refracted and vertically incident.
Further, the structurization pattern 5a is integrally formed on the upper surface of the base portion 5b, and has a structure for vertically refracting and emitting the light that is incident through the base portion 5b. 
The structurization pattern 5a is generally formed so that its cross-section has a triangular shape, and an apex angle of the triangular shape is usually approximately 90 degrees.
Moreover, the second optical sheet 6 has the same shape as the first optical sheet 5, and secondarily condenses and releases the light that is primarily condensed by the first optical sheet 5 so as to increase the brightness of the light.
Here, the first optical sheet 5 and the second optical sheet 6 are disposed so as to further increase the brightness such that an extension direction of the structurization pattern of the first optical sheet 5 and an extension direction of the structurization pattern of the second optical sheet 6 intersect with each other at a right angle.
Moreover, the reflective polarizing sheet 7 is formed above the second optical sheet 6 to serve to transmit light polarized in the first direction of the light incident from the optical sheet 6 and reflect light polarized in the second direction. Meanwhile, reference numeral 8 in the drawings indicates a liquid crystal panel.
In the back light element of the configuration as described above, there has been a problem in which mountain grinding or the like of the structurization pattern due to the contact between the first optical sheet 5 and the second optical sheet 6 occurs to lower the quality of the display.